Substrate processing apparatus

ABSTRACT

A substrate processing apparatus includes: a cylindrical shaped chamber configured to accommodate a substrate; a movable electrode capable of moving along a central axis of the cylindrical shaped chamber within the cylindrical shaped chamber; a facing electrode facing the movable electrode within the cylindrical shaped chamber; and an expansible/contractible partition wall connecting the movable electrode with an end wall on one side of the cylindrical shaped chamber. In the substrate processing apparatus, a high frequency power is applied to a first space between the movable electrode and the facing electrode, a processing gas is introduced thereto, and the movable electrode is not in contact with a sidewall of the cylindrical shaped chamber. At least one low dielectric member is provided in a second space between the movable electrode and the end wall on one side of the cylindrical shaped chamber.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No.2009-081898 filed on Mar. 30, 2009, and U.S. Provisional ApplicationSer. No. 61/242,603 filed on Sep. 15, 2009, the entire disclosures ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to a substrate processing apparatus. Inparticular, the present disclosure relates to a substrate processingapparatus including a movable electrode in a processing chamber.

BACKGROUND OF THE INVENTION

A substrate processing apparatus, which performs a plasma process on asemiconductor wafer (hereinafter, simply referred to as “wafer”) servingas a substrate, includes a chamber (processing chamber) thataccommodates a wafer and can be depressurized; a susceptor positioned onthe lower part within the chamber; and a shower head (upper electrode)provided within the chamber to face the susceptor. The susceptor isconfigured to mount thereon the wafer and serves as an electrodeapplying a high frequency power from a connected high frequency powersupply into the chamber. The shower head introduces a processing gasinto the chamber and is grounded to serve as a ground electrode. In thissubstrate processing apparatus, the processing gas supplied into thechamber is excited into plasma by the high frequency power and the waferis plasma-processed by the plasma.

However, in order to appropriately distribute the plasma within thechamber, particularly, in a space between the shower head and thesusceptor, there has been developed a substrate processing apparatushaving a movable susceptor, thereby adjusting a thickness (hereinafter,referred to as a “gap”) of a processing space between the shower headand the susceptor (see, for example, Patent Document 1). Besides, onaccount of the restriction on the layout around the substrate processingapparatus, a substrate processing apparatus having a movable showerhead, not the movable susceptor, is recently under development.

FIG. 12 is a cross sectional view schematically illustrating aconfiguration of a substrate processing apparatus having a movableshower head.

In a substrate processing apparatus 100 of FIG. 12, a shower head 103 isinstalled within a cylindrical chamber 101 so as to face a susceptor102. The shower head 103 is formed into a substantially circular plateshape having an outer diameter substantially the same as an innerdiameter of the chamber 101. The shower head 103 is configured tovertically move like a piston in the chamber 101 by a non-illustratedlift mechanism. Further, installed between the shower head 103 and aceiling portion of the chamber 101 is a bellows 104 expansible andcontractible along with the vertical movement of the shower head 103.The bellows 104 seals the inside of the chamber 101 from its surroundingair. Furthermore, in FIG. 12, the shower head 103 at the lowermostposition is indicated by a solid line, and the shower head 103 at theuppermost position is indicated by a dashed line.

Patent Document 1: Pamphlet of International Patent Publication No.WO03/003437 (FIG. 1)

However, this substrate processing apparatus 100 is configured to keepsome gap between the shower head 103 and a sidewall 101 b of the chamber101, so that the shower head 103 smoothly moves up and down, therebypreventing generation of particles caused by a friction between theshower head 103 and the sidewall 101 b. That is, since the shower head103 is not in contact with the sidewall 101 b, a direct current may notbe flown from the shower head 103 to the sidewall 101 b and analternating current may be hardly flown from the shower head 103 to thesidewall 101 b. Accordingly, in the substrate processing apparatus 100,a high frequency current caused by a high frequency power applied to thesusceptor 102 flows through the susceptor 102, the processing space, theshower head 103, the bellows 104, a ceiling wall 101 a of the chamber101, and the sidewall 101 b of the chamber 101 in sequence, as depictedby the arrow in FIG. 12.

The bellows 104 is made of stainless steel for increasing durability andhas higher impedance than that of the other parts (e.g., the chamber101, the shower head 103, and the like) made of aluminum. Accordingly, apotential difference is generated along the bellows 104, to be specific,between the shower head 103 and the ceiling wall 101 a of the chamber101. Therefore, there are concerns that an electric field may begenerated in a space (hereinafter, referred to as “upper space”) USbetween the shower head 103 and the ceiling wall 101 a.

This electric field ionizes a processing gas introduced into the upperspace US from the gap, so that plasma is generated. However, there is aproblem in that the plasma generated in the upper space US erodes wallsurfaces of the chamber 101 or the shower head 103, and forms a deposit.

BRIEF SUMMARY OF THE INVENTION

In view of the foregoing, the present disclosure provides a substrateprocessing apparatus capable of preventing generation of plasma in aspace between a movable electrode and an end wall on one side of acylindrical shaped chamber.

In order to solve the above-mentioned problem, in accordance with oneaspect of the present disclosure, there is provided a substrateprocessing apparatus including a cylindrical shaped chamber configuredto accommodate a substrate; a movable electrode capable of moving alonga central axis of the cylindrical shaped chamber within the cylindricalshaped chamber; a facing electrode facing the movable electrode withinthe cylindrical shaped chamber; and an expansible/contractible partitionwall connecting the movable electrode with an end wall on one side ofthe cylindrical shaped chamber. In the substrate processing apparatus, ahigh frequency power is applied to a first space between the movableelectrode and the facing electrode, a processing gas is introducedthereto, and the movable electrode is not in contact with a sidewall ofthe cylindrical shaped chamber. At least one low dielectric member isprovided in a second space between the movable electrode and the endwall on one side of the cylindrical shaped chamber.

Further, in the substrate processing apparatus, the low dielectricmember may be provided on at least one of the movable electrode and theend wall on one side of the cylindrical shaped chamber.

In the substrate processing apparatus, a dielectric constant of the lowdielectric member may be about 10 or less.

In the substrate processing apparatus, the low dielectric member may bemade of polytetrafluoroethylene (PTFE), a copolymer oftetrafluoroethylene and perfluoroalkyl vinyl ether (PFA) orpolychlorotrifluoroethylene (PCTFE).

Furthermore, in the substrate processing apparatus, another dielectricmember may be further installed between the sidewall of the cylindricalshaped chamber and the movable electrode.

In the substrate processing apparatus, a thickness of the anotherdielectric member may be equal to or greater than about 5 mm in adirection from the movable electrode to the sidewall.

In the substrate processing apparatus, the another dielectric member maybe made of ceramic.

In the substrate processing apparatus, the another dielectric member maybe installed at the movable electrode.

In the substrate processing apparatus, the another dielectric member maybe installed at the sidewall.

Further, in accordance with another aspect of the present disclosure,there is provided a substrate processing apparatus including acylindrical shaped chamber configured to accommodate a substrate; amovable electrode capable of moving along a central axis of thecylindrical shaped chamber within the cylindrical shaped chamber; afacing electrode facing the movable electrode within the cylindricalshaped chamber; and an expansible/contractible partition wall connectingthe movable electrode with an end wall on one side of the cylindricalshaped chamber. In the substrate processing apparatus, a high frequencypower is applied to a first space between the movable electrode and thefacing electrode, a processing gas is introduced thereto, and themovable electrode is not in contact with a sidewall of the cylindricalshaped chamber. Moreover, a first dielectric member is provided at thecylindrical shaped chamber's sidewall facing the movable electrode, andan overlap area between the first dielectric member and a side surfaceof the movable electrode is changed according to movement of the movableelectrode.

In the substrate processing apparatus, a second dielectric member may beprovided at the movable electrode's side surface facing the firstdielectric member and an overlap area between the first dielectricmember and the second dielectric member may be changed according tomovement of the movable electrode.

In the substrate processing apparatus, in a cross section of the firstdielectric member along a central axis of the cylindrical shapedchamber, a width in a direction orthogonal to the central axis may beconstant along the central axis.

In the substrate processing apparatus, in a cross section of the firstdielectric member along a central axis of the cylindrical shapedchamber, a width in a direction orthogonal to the central axis may begradually changed along the central axis.

In the substrate processing apparatus, in a cross section of the seconddielectric member along a central axis of the cylindrical shapedchamber, a width in a direction orthogonal to the central axis may beconstant along the central axis.

In the substrate processing apparatus, in a cross section of the seconddielectric member along a central axis of the cylindrical shapedchamber, a width in a direction orthogonal to the central axis may begradually changed along the central axis.

In the substrate processing apparatus, each of the first dielectricmember and the second dielectric member may be made of quartz, ceramicor an insulating resin.

In the above-mentioned substrate processing apparatus, at least one lowdielectric member is provided in the second space between the movableelectrode and the end wall on one side of the cylindrical shapedchamber. Thus, a voltage drop related to a high frequency current causedby the high frequency power applied to the first space and flowingthrough the movable electrode, the second space, the end wall on oneside of the cylindrical shaped chamber, and the sidewall of this chambercan be shared by the low dielectric member. Accordingly, a voltage dropin the second space can be reduced and a potential difference in thesecond space can be reduced. As a result, it is possible to suppressgeneration of an electric field in the space (the second space) betweenthe movable electrode and the end wall on one side of the cylindricalshaped chamber and further suppress generation of plasma therein.

In the substrate processing apparatus, the low dielectric member isprovided on at least one of the movable electrode and the end wall onone side of the cylindrical shaped chamber, and, thus, the configurationof the substrate processing apparatus can be simplified. Accordingly, itis possible to easily assemble the substrate processing apparatus.

In the substrate processing apparatus, a dielectric constant of the lowdielectric member is equal to or less than about 10. Therefore, it ispossible to appropriately adjust a voltage drop to be shared by the lowdielectric member.

In the substrate processing apparatus, the low dielectric member is madeof polytetrafluoroethylene, a copolymer of tetrafluoroethylene andperfluoroalkyl vinyl ether or polychlorotrifluoroethylene. Thesematerials have a high resistance to radicals, and, thus, even if aradical is introduced into the second space from the first space, it ispossible to prevent the low dielectric member from being eroded.Further, it is easy to obtain these materials and, thus, the substrateprocessing apparatus can be easily manufactured, thereby reducingmanufacturing cost.

Moreover, in the substrate processing apparatus, another dielectricmember is further installed between the sidewall of the cylindricalshaped chamber and the movable electrode. Thus, the sidewall of thecylindrical shaped chamber can be spaced from the movable electrode, sothat it is possible to prevent generation of abnormal electric dischargebetween the sidewall of the cylindrical shaped chamber and the movableelectrode. Further, since a gap between the sidewall of the cylindricalshaped chamber and the movable electrode is filled up with the anotherdielectric member, it is possible to prevent plasma generated in thefirst space from being introduced into the second space.

In the substrate processing apparatus, a thickness of the anotherdielectric member is equal to or greater than about 5 mm in a directionfrom the movable electrode to the sidewall. Thus, it is possible tosecurely separate the sidewall of the cylindrical shaped chamber fromthe movable electrode.

In the substrate processing apparatus, the another dielectric member ismade of ceramic. Even though the another dielectric member is in contactwith the first space, ceramic has a high resistance to radicals and ahigh resistance to ion-sputtering. Therefore, it is possible to preventthe another dielectric member from being eroded by the plasma generatedin the first space.

In the substrate processing apparatus, the another dielectric member isinstalled at the movable electrode. Thus, even if this movable electrodemoves, the another dielectric member is always positioned between thesidewall of the cylindrical shaped chamber and the movable electrode.Therefore, it is possible to securely prevent generation of abnormalelectric discharge.

In the substrate processing apparatus, the another dielectric member isinstalled at the sidewall, and, thus, a configuration of the movableelectrode can be simplified.

In the substrate processing apparatus, the first dielectric member isprovided at the cylindrical shaped chamber's sidewall facing the movableelectrode, and the overlap area between the first dielectric member andthe side surface of the movable electrode is changed according tomovement of the movable electrode. Therefore, the electrostaticcapacitance of an electrostatic coupling between the movable electrode,the first dielectric member, and the sidewall of the cylindrical shapedchamber is changed according to a change in the gap, and, thus, plasmadistribution in the processing space according to the change in the gapcan be optimized.

In the substrate processing apparatus, the second dielectric member isprovided at the movable electrode's side surface facing the firstdielectric member and the overlap area between the first dielectricmember and the second dielectric member is changed according to movementof the movable electrode. Therefore, the electrostatic capacitance isfinely changed, and, thus, plasma distribution in the processing spacecan be more finely adjusted according to the change in the gap.

In the cross section of the first or second dielectric member along thecentral axis of the cylindrical shaped chamber, the width in thedirection orthogonal to the central axis is constant along the centralaxis. Therefore, the overlap area between the movable electrode and thefirst dielectric member or the overlap area between the first dielectricmember and the second dielectric member is changed according to thechange in the gap, and based on the change in the overlap area, thecapacitance of the ground path of the high frequency current is changed.Accordingly, by adjusting a capacitance distribution ratio between theground path and another ground path, plasma distribution in theprocessing space can be optimized.

In the cross section of the first or second dielectric member along thecentral axis of the cylindrical shaped chamber, the width in thedirection orthogonal to the central axis is gradually changed along thecentral axis. Therefore, the overlap area between the movable electrodeand the first dielectric member or the overlap area between the firstdielectric member and the second dielectric member is changed accordingto the change in the gap, and based on the change in the overlap areaand a change in the width of the first dielectric member and/or thesecond dielectric member in a direction orthogonal to the central axis,a capacitance of a ground path of the high frequency current is changed.Accordingly, by adjusting a capacitance distribution ratio between theground path and the another ground path, plasma distribution in theprocessing space can be optimized.

In the substrate processing apparatus, each of the first dielectricmember and the second dielectric member is made of quartz, ceramic orthe insulating resin. Therefore, they have a resistance toion-sputtering as well as a resistance to radicals, and, thus, the firstdielectric member and the second dielectric member can be prevented frombeing eroded by plasma generated in the processing space.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may best be understood by reference to the followingdescription taken in conjunction with the following figures:

FIG. 1 is a schematic cross-sectional view of a substrate processingapparatus in accordance with a first embodiment of the presentinvention;

FIG. 2 is a view showing an electric circuit representing an upper spaceof the substrate processing apparatus of FIG. 1;

FIGS. 3A and 3B are schematic cross-sectional views of a first modifiedexample and a second modified example of the substrate processingapparatus of FIG. 1, respectively;

FIG. 4 is a schematic cross-sectional view of a substrate processingapparatus in accordance with a second embodiment of the presentinvention;

FIG. 5 is a schematic cross-sectional view of a modified example of thesubstrate processing apparatus of FIG. 4;

FIG. 6 is a schematic cross-sectional view of a substrate processingapparatus in accordance with a third embodiment of the presentinvention;

FIGS. 7A to 7D are schematic diagrams showing overlap statuses between ashower head and a first dielectric member of FIG. 6;

FIGS. 8A to 8D are views of a modified example of an electrostaticcoupling between a shower head, a dielectric member, and a sidewall of achamber in the third embodiment;

FIGS. 9A to 9D are views of another modified example of an electrostaticcoupling between a shower head, a dielectric member, and a sidewall of achamber in the third embodiment;

FIGS. 10A to 10D are views of still another modified example of anelectrostatic coupling between a shower head, a dielectric member, and asidewall of a chamber in the third embodiment;

FIGS. 11A to 11D are views of still another modified example of anelectrostatic coupling between a shower head, a dielectric member, and asidewall of a chamber in the third embodiment; and

FIG. 12 is a schematic cross-sectional view of a substrate processingapparatus including a movable shower head.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings.

Above all, there will be explained a substrate processing apparatus inaccordance with a first embodiment of the present invention.

FIG. 1 is a schematic cross-sectional view of a substrate processingapparatus in accordance with the first embodiment. This substrateprocessing apparatus is configured to perform a dry etching process on awafer.

As illustrated in FIG. 1, a substrate processing apparatus 10 includes acylindrical chamber (cylindrical shaped vessel) 11 accommodating a waferW of, e.g., about 300 mm in diameter. Further, a circular plate-shapedsusceptor (facing electrode) 12 mounting thereon the wafer W for asemiconductor device is installed at the lower part of the chamber 11.The chamber 11 includes a circular pipe-shaped sidewall 13 and acircular plate-shaped cover (an end wall on one side of the cylindricalshaped vessel) 14 which covers an upper end of the sidewall 13.

The inside of the chamber 11 is depressurized by a TMP (Turbo MolecularPump) and a DP (Dry Pump) (both not illustrated), and an internalpressure of the chamber 11 is controlled by an APC valve (notillustrated).

The susceptor 12 is connected with a first high frequency power supply15 via a first matching unit 16 and with a second high frequency powersupply 17 via a second matching unit 18. The first high frequency powersupply 15 is configured to apply a high frequency bias power having arelatively low frequency of, e.g., about 3.2 MHz to the susceptor 12.The second high frequency power supply 17 is configured to apply aplasma-generating high frequency power having a relatively highfrequency of, e.g., about 100 MHz to the susceptor 12. The susceptor 12is configured to apply the plasma-generating power to the inside of thechamber 11.

Installed at the upper part of the susceptor 12 is an electrostaticchuck 20 including therein an electrostatic electrode plate 19. Theelectrostatic chuck 20 is made of a ceramic member having a circularplate shape, and the electrostatic electrode plate 19 is connected witha DC power supply 21. If a positive DC voltage is supplied to theelectrostatic electrode plate 19, a negative potential is generated onthe wafer W's surface (hereinafter, referred to as “rear surface”)facing the electrostatic chuck 20. As a result, a potential differenceis generated between the electrostatic electrode plate 19 and the rearsurface of the wafer W. Accordingly, the wafer W is attracted to andheld on the electrostatic chuck 20 by Coulomb force or Johnson-Rahbekforce caused by the potential difference.

Further, a ring-shaped focus ring 22 is mounted on the susceptor 12 soas to surround the wafer W attracted to and held on the electrostaticchuck 20. The focus ring 22 is made of a conductive material such assingle crystalline silicon which is the same material as that of thewafer W. Since the focus ring 22 is made of the conductive material,plasma can be distributed not only on the wafer W but also on the focusring 22. Therefore, a plasma density on a peripheral portion of thewafer W can be maintained at the substantially same level as a plasmadensity on a central portion of the wafer W. Accordingly, it is possibleto maintain uniformity of the dry etching process to be performed on theentire surface of the wafer W.

A shower head (movable electrode) 23 is installed to face the susceptor12 at the upper part inside the chamber 11. The shower head 23 includesa conductive upper electrode plate 25 formed into a circular plate shapeand having a plurality of gas holes 24; a cooling plate 26attachably/detachably holding the upper electrode plate 25; a shaft 27holding the cooling plate 26; and a processing gas container 28positioned at the upper end of the shaft 27. The shower head 23 isgrounded via the cover 14 and the sidewall 13 and serves as a groundelectrode for a plasma-generating power applied to the inside of thechamber 11.

The shaft 27 includes a gas path 29 penetrating the inside of the shaft27 in a vertical direction of the drawing, and the cooling plate 26includes therein a buffer room 30. The gas path 29 connects theprocessing gas container 28 with the buffer room 30, and the buffer room30 is communicated with the inside of the chamber 11 through each gashole 24. In the shower head 23, the gas holes 24, the processing gascontainer 28, the gas path 29, and the buffer room 30 constitute aprocessing gas introducing unit. Further, this processing gasintroducing unit introduces the processing gas supplied to theprocessing gas container 28 into the chamber 11, to be specific, to aprocessing space PS (a first space) between the shower head 23 and thesusceptor 12.

Since an outer diameter of the upper electrode plate 25 of the showerhead 23 is set to be a bit smaller than an inner diameter of the chamber11, the shower head 23 is not in contact with the sidewall 13. That is,the shower head 23 is installed within the chamber 11 in a movablestate. The shaft 27 penetrates the cover 14 and an upper portion of theshaft 27 is connected with a lift mechanism (not illustrated) positionedabove the substrate processing apparatus 10. The lift mechanism isconfigured to move the shaft 27 in a vertical direction of the drawing.Here, the shower head 23 vertically moves along a central axis of thechamber 11 like a piston. Accordingly, a gap, i.e., a thickness of theprocessing space PS, between the shower head 23 and the susceptor 12 canbe adjusted. The maximum moving distance of the shower head 23 in thevertical direction of the drawing is about 70 mm, for example.

Particles may be generated due to a friction between the shaft 27 andthe cover 14. Therefore, a side surface of the shaft 27 is covered by,e.g., a bellows 31. The bellows is an expansible/contractible pressurepartition wall made of, e.g., stainless steel. One end of the bellows 31is joined to the cover 14 and the other end thereof is joined to theshower head 23. Further, the bellows 31 seals the inside of the chamber11 from the outside of the chamber 11.

In the substrate processing apparatus 10, the processing gas supplied tothe processing gas container 28 is introduced into the processing spacePS through the processing gas introducing unit, and the introducedprocessing gas is excited into plasma by the plasma-generating powerapplied to the processing space PS. Positive ions in the plasma areattracted toward the wafer W mounted on the susceptor 12 by a negativebias potential caused by a bias power applied to the susceptor 12, and adry etching process is performed on the wafer W.

The operations of respective components such as the first high frequencypower supply 15 or the second high frequency power supply 17 of thesubstrate processing apparatus 10, are controlled by a CPU of acontroller (not illustrated) provided in the substrate processingapparatus according to a program corresponding to a dry etching process.

In the substrate processing apparatus 10, the shower head 23 is not incontact with the sidewall 13. Thus, a high frequency current caused bythe plasma-generating power applied to the processing space PS flowsthrough the shower head 23, the upper space US, the cover 14, and thesidewall 13 and reaches a ground. Here, since the bellows 31 has highimpedance, a potential difference is generated between the shower head23 and the cover 14. Therefore, an electric field may be generated inthe upper space US (a second space) between the shower head 23 and thecover 14.

In accordance with the present embodiment, a voltage drop in the upperspace US is reduced. To be specific, there is installed a firstcapacitor layer 32 made of a low dielectric constant material on theshower head 23's surface facing the upper space US, and there isinstalled a second capacitor layer 33 made of a low dielectric constantmaterial on the cover 14's surface facing the upper space US. Here, thespace between the shower head 23 and the cover 14 can be represented byan electrical series circuit of three capacitors as depicted in FIG. 2.A capacitor formed of the first capacitor layer 32 is denoted by C₁, acapacitor formed of the second capacitor layer 33 is denoted by C₂, anda capacitor formed of the upper space US is denoted by C₃. If a voltagedrop at the capacitor C₁ or the capacitor C₂ is increased, a voltagedrop at the capacitor C₃ can be relatively decreased, thereby reducingthe potential difference in the upper space US.

Desirably, the first capacitor layer 32 and the second capacitor layer33 may be made of a material having a dielectric constant of about 10 orless. Thus, the voltage drop to be shared by the first capacitor layer32 or the second capacitor layer 33 can be appropriately adjusted. As amaterial of the first capacitor layer 32 or the like, it is possible touse an insulating resin such as polytetrafluoroethylene (PTFE), acopolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (PFA) orpolychlorotrifluoroethylene (PCTFE); an engineering plastic-based resin;quartz (SiO₂); alumina ceramic (Al₂O₂); aluminum nitride (AlN); andsilicon nitride (SiN). In particular, polytetrafluoroethylene, thecopolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, andpolychlorotrifluoroethylene have a high resistance to radicals.Therefore, even if plasma is introduced into the upper space US from theprocessing space PS, it is possible to prevent the first capacitor layer32 or the second capacitor layer 33 from being eroded by using thesematerials having a high resistance to radicals.

In the substrate processing apparatus in accordance with the presentembodiment, the first capacitor layer 32 and the second capacitor layer33 are provided in the upper space US between the shower head 23 and thecover 14. Thus, a voltage drop related to a high frequency currentcaused by a high frequency power applied to the processing space PS andflowing through the shower head 23, the upper space US, the cover 14,and the sidewall 13 is shared by the first capacitor layer 32 and thesecond capacitor layer 33. Accordingly, a voltage drop in the upperspace US can be reduced and a potential difference in the upper space UScan be reduced. As a result, it is possible to suppress generation of anelectric field in the upper space US and further suppress generation ofplasma therein. Therefore, it is possible to prevent the cover 14 or theshower head 23 of the chamber 11 from being eroded and further preventgeneration of deposits (particles) in the upper space US.

Further, in the substrate processing apparatus 10, the first capacitorlayer 32 is installed on the shower head 23 and the second capacitorlayer 33 is installed on the cover 14, and, thus, a configuration of thesubstrate processing apparatus 10 can be simplified. Therefore, thesubstrate processing apparatus 10 may be easily assembled.

In the above-described substrate processing apparatus 10, two capacitorlayers are provided in the upper space US, but the number of thecapacitor layers is not limited. Even if there is installed onecapacitor layer therein, the voltage drop can be shared by the capacitorlayer, and, thus, at least one capacitor may be installed in the upperspace US. For example, in the upper space US, only the second capacitorlayer 33 may be provided on the cover 14 (see FIG. 3A), or only thefirst capacitor layer 32 may be provided on the shower head 23 (see FIG.3B).

In the first embodiment, there has been explained a case where theshower head 23 moves and there exists the upper space US between theshower head 23 and the cover 14. However, in the case where thesusceptor moves and there exists a lower space between the susceptor anda bottom wall of the chamber, at least one capacitor layer may beprovided in the lower space, thereby suppressing generation of anelectric field in the lower space and further suppressing generation ofplasma therein.

Hereinafter, there will be explained a substrate processing apparatus inaccordance with a second embodiment of the present invention.

The present embodiment is basically the same as the first embodiment inview of a configuration or an operation but different from the firstembodiment only in that a low dielectric member is installed between ashower head and a sidewall of a chamber. Therefore, redundantdescription of the same will be omitted, but only differentconfiguration and operation will be explained.

As described in the first embodiment, in a substrate processingapparatus including therein a movable shower head, the shower head isnot in contact with a sidewall. However, in order to prevent plasma fromintroducing into an upper space from a processing space, a gap betweenthe shower head (an upper electrode plate) and the sidewall is set to aminimum value and the conductive upper electrode plate becomes close toa sidewall in a ground potential. Since two objects having a highpotential difference therebetween are close to each other, there is arisk of generation of abnormal electric discharge. In order to lower therisk, the upper electrode plate and the sidewall are separated from eachother in the present embodiment.

FIG. 4 is a schematic cross-sectional view of a substrate processingapparatus in accordance with the present embodiment.

As depicted in FIG. 4, a substrate processing apparatus 40 includes ashower head 41, and the shower head 41 includes a circular plate-shapedupper electrode plate 43 of which an outer periphery is surrounded by adielectric ring (another dielectric member) 42; a cooling plate 26attachably/detachably holding the upper electrode plate 43. Thedielectric ring 42 is provided at the upper electrode plate 43 and hasthe thickness of about 5 mm or more in a direction from the shower head41 to a sidewall 13. The dielectric ring 42 is configured to separatethe upper electrode plate 43 from the sidewall 13. With thisconfiguration, it is possible to prevent generation of abnormal electricdischarge between the sidewall 13 and the shower head 41.

Further, a gap between the dielectric ring 42 and the sidewall 13 is setto be in the range from about 0.5 mm to about 3.0 mm. Thus, even if thedielectric ring 42 or the sidewall 13 is thermally expanded, they do notinterfere with each other, and a gap between the sidewall 13 and theupper electrode plate 43 is almost filled with the dielectric ring 42.Accordingly, it is possible to prevent plasma generated in a processingspace PS from introducing into an upper space US.

The upper electrode plate 43, the dielectric ring 42, and the sidewall13 form a capacitor and are capacitively-coupled to each other toprovide a small capacitance. Thus, a part of a high frequency currentcaused by a plasma-generating power applied to the processing space PSflows through the upper electrode plate 43, the dielectric ring 42, andthe sidewall 13, and reaches a ground. That is, the high frequencycurrent can be divided into one flowing through the upper space US andthe other flowing through the dielectric ring 42. Accordingly, the highfrequency current flowing through the upper space US can be decreased,thereby reducing a potential difference in the upper space US.

The dielectric ring 42 is exposed to plasma generated in the processingspace PS, and, thus, a material of the dielectric ring 42 needs to havea resistance to ion-sputtering as well as a resistance to radicals. Itis desirable to use quartz or a ceramic-based material such as aluminaceramic, aluminum nitride, silicon nitride, yttria (Y₂O₃), sapphire, andzirconia. It may be also possible to use an insulating resin such aspolytetrafluoroethylene or an engineering plastic-based resin coatedwith a plasma-resistant material. Further, a dielectric constant of thedielectric ring 42 may be in a range from about 2 to about 30.

In the above-described substrate processing apparatus 40, although thedielectric ring 42 is installed at an outer periphery of the upperelectrode plate 43, as depicted in FIG. 5, a cylindrical dielectricmember 44 may be installed at a sidewall 13 instead of the dielectricring 42. In this case, the dielectric member 44 separates an upperelectrode plate 25 from the sidewall 13, and, thus, it is possible toprevent generation of abnormal electric discharge between the sidewall13 and a shower head 23.

Further, in the second embodiment, there has been explained a case wherethe shower head 41 moves and there exists a gap between the shower head41 and the sidewall 13. However, in the case where a susceptor moves andthere exists a gap between the susceptor and the sidewall 13, byinstalling a dielectric member to fill the gap, it is possible toprevent generation of abnormal electric discharge between the sidewall13 and the susceptor.

Hereinafter, there will be explained an experimental example of thepresent invention.

Experimental Example

In the substrate processing apparatus 10, the first capacitor layer 32was formed by stacking two Teflon (registered trademark) sheets eachhaving the thickness of about 1 mm; the second capacitor layer 33 wasformed of one Teflon (registered trademark) sheet having a thickness ofabout 1 mm; a plasma-generating power having a predetermined value wasapplied to the processing space PS without applying a bias powerthereto; and a thickness of the processing space PS (gap) was set to apredetermined value. Then, it was checked whether or not plasma wasgenerated in the upper space US. A result thereof is shown in Table 1below.

TABLE 1 Gap Plasma- thickness generating (mm) power (W) 15 40 85 500 ◯ ◯◯ 1000 ◯ ◯ ◯ 1500 ◯ ◯ ◯ 2000 ◯ ◯ ◯ 2500 ◯ ◯ ◯ The mark “◯” in Table 1represents that plasma is not generated.

Comparative Example

In the substrate processing apparatus 10, the capacitor layer in theupper space US was not installed; a plasma-generating power having apredetermined value was applied to the processing space PS withoutapplying a bias power thereto; a thickness of the processing space PS(gap) was set to a predetermined value. Then, it was checked whether ornot plasma was generated in the upper space US. A result thereof isshown in Table 2 below.

TABLE 2 Plasma- Gap generating thickness power (mm) (W) 15 40 85 500 Δ ◯◯ 1000 ◯ ◯ X 1500 Δ ◯ X 2000 ◯ X X 2500 X X X The mark “X” in Table 2represents that plasma is generated, the mark “Δ” represents that plasmais sometimes generated, and the mark “◯” represents that plasma is notgenerated.

As can be seen from comparison of Table 1 and Table 2, it is possible tosecurely prevent generation of plasma by installing the first capacitorlayer 32 and the second capacitor 33 in the upper space US.

Hereinafter, there will be explained a substrate processing apparatus inaccordance with a third embodiment of the present invention.

In this substrate processing apparatus, an electrostatic coupling isformed between a movable electrode and a cylindrical shaped chamber'ssidewall facing the movable electrode. Further, a ground path of a highfrequency current caused by a high frequency power applied to asusceptor includes a line (hereinafter, referred to as “first groundpath”) to be grounded along the movable electrode, an upper space US,and a cover and a sidewall of the chamber and a line (hereinafter,referred to as “second ground path”) to be grounded along the movableelectrode and the sidewall of the chamber. Furthermore, a capacitancedistribution ratio of the ground paths is changed according to movementof the movable electrode.

In a substrate processing apparatus performing a predetermined plasmaprocess onto a wafer, multiple plasma processes may be consecutivelyperformed as a batch process in one chamber. Here, since a processingcondition, particularly an optimum position of a shower head serving asa movable electrode, is different in each process, an optimum gap is setfor each process. In such a batch process, whenever the gap is changed,desirably, optimization of plasma distribution in a processing space PSmay be required, and, thus, there has been a demand for development in atechnology of increasing parameters for optimizing the plasmadistribution.

To satisfy such a demand, the present embodiment provides a substrateprocessing apparatus capable of optimizing plasma distribution in aprocessing space according to a change in a gap.

In accordance with the present embodiment, there is provided a substrateprocessing apparatus including a cylindrical shaped chamber configuredto accommodate a substrate, a movable electrode capable of moving alonga central axis of the cylindrical shaped chamber within the cylindricalshaped chamber, a facing electrode facing the movable electrode withinthe cylindrical shaped chamber, and an expansible/contractible partitionwall connecting the movable electrode with an end wall on one side ofthe cylindrical shaped chamber. Further, a high frequency power isapplied to a first space between the movable electrode and the facingelectrode and a processing gas is introduced thereto. Furthermore, themovable electrode is not in contact with a sidewall of the cylindricalshaped chamber, and a first dielectric member is provided at thecylindrical shaped chamber's sidewall facing the movable electrode, andan overlap area between the first dielectric member and a side surfaceof the movable electrode is changed according to movement of the movableelectrode.

FIG. 6 is a schematic cross-sectional view of a substrate processingapparatus in accordance with a third embodiment of the presentinvention.

In FIG. 6, a basic configuration of a substrate processing apparatus 50is the same as that of the substrate processing apparatus (see FIG. 1)in accordance with the first embodiment. Therefore, redundantdescription of the same will be omitted and the present embodiment willbe explained below focusing on different configuration and operation.

In a substrate processing apparatus, plasma distribution in a processingspace PS of a chamber is affected by, e.g., a gap, a pressure within thechamber, a kind of a processing gas, and an application value of a highfrequency power.

The substrate processing apparatus in accordance with the presentembodiment is provided to obtain plasma distribution. Here, a basicprocessing condition, which is determined by a process purpose butcannot be modified in order to achieve the process purpose, ismaintained as it is and other processing conditions more appropriate forthe process are set in addition to such a basic condition. In order todo so, a dielectric member is provided at a sidewall of the cylindricalshaped chamber, and an electrostatic coupling is formed between thesidewall of the chamber, the dielectric member provided at thissidewall, and a movable electrode facing thereto. In this case, anelectrostatic capacitance of the electrostatic coupling is changedaccording to movement of the movable electrode. Therefore, a capacitanceof the second ground path and a capacitance distribution ratio betweenthe second ground path and the first ground path are changed, so thatplasma distribution in the processing space PS can be optimized.

The substrate processing apparatus 50 is different from the substrateprocessing apparatus 10 of FIG. 1 in that the first capacitor layer 32and the second capacitor layer made of a low dielectric constantmaterial on the surfaces facing the upper space US are omitted and afirst dielectric member 55 is installed at a chamber 11's sidewall 53facing a shower head 51 serving as a movable electrode.

That is, the substrate processing apparatus 50 includes thecylindrical-shaped chamber (cylindrical shaped vessel) 11 and the showerhead (movable electrode) 51 which can be moved along a central axis ofthe chamber 11, and the first dielectric member 55 is installed at thechamber 11's sidewall 53 facing the shower head 51.

The first dielectric member 55 is of a ring shape and inserted andfitted into a ring-shaped recess of a predetermined depth installed atthe sidewall 53 of the cylindrical chamber 11. A cross section of thefirst dielectric member 55 along the central axis of the chamber 11 has,for example, a rectangular shape. Therefore, the first dielectric member55's width (hereinafter, referred to as “thickness”) in a directiontoward the central axis of the chamber 11 is constant along the centralaxis of the chamber 11. The first dielectric member 55 faces a sidesurface of the shower head 51 with a gap G therebetween and anoverlapped area sandwiching the gap G (hereinafter, simply referred toas “overlap area”) is changed according to movement of the shower head51.

Further, in FIG. 6, a length of the first dielectric member 55 along thecentral axis of the chamber 11 is the same as a thickness of the showerhead 51 but it is not limited thereto. The length of the firstdielectric member 55 can be appropriately selected.

FIGS. 7A to 7D are schematic diagrams showing overlap statuses betweenthe shower head 51 and the first dielectric member 55 of FIG. 6.

In FIGS. 7A to 7D, in a status where the shower head 51 is at thelowermost position in a range of a vertical movement of the shower head51, i.e., in a status with the smallest gap (see FIG. 7A), an overlaparea between the first dielectric member 55 and the shower head 51becomes largest. If this area is defined as 1.0, in a status where theshower head 51 arrives at the middle point between the lowermostposition and the uppermost position (see FIG. 7B) by gradually movingupward, an overlap area becomes 0.5. Further, in a status where theshower head 51 arrives at the uppermost position (see FIG. 7C), anoverlap area becomes 0.

FIG. 7D is a view showing a change of electrostatic capacitance of theelectrostatic coupling between the shower head 51, the first dielectricmember 55, and the sidewall 53 of the chamber 11. In FIG. 7D, theelectrostatic capacitance varies depending on a position of the showerhead 51. That is, as the shower head 51 moves upward, the electrostaticcapacitance gradually increases.

In accordance with the present embodiment, the ring-shaped firstdielectric member 55 is provided at the chamber 11's sidewall 53 facingthe shower head 51 and the overlap area between the first dielectricmember 55 and the side surface of the shower head 51 is changedaccording to movement of the shower head 51. Accordingly, theelectrostatic capacitance of the electrostatic coupling between theshower head 51, the first dielectric member 55, and the sidewall 53 ofthe chamber 11 is changed according to movement of the shower head 51.Therefore, the capacitance of the second ground path flowing through theshower head 51, the sidewall 53 of the chamber 11 to the ground ischanged. Further, if the capacitance of the second ground path ischanged, the capacitance distribution ratio between the second groundpath and the first ground path is changed and, particularly, a value ofa high frequency current flowing through a peripheral end portion of theshower head 51 is changed, and, thus, plasma distribution in theprocessing space PS becomes changed.

Accordingly, a capacitance distribution ratio between the first groundpath and the second ground path for obtaining a required plasmadistribution in a first processing space PS is calculated with respectto a gap in each plasma process. Then, a position at the sidewall 53 ofthe chamber 11, a shape of a cross section, and a thickness of the firstdielectric member 55 for obtaining the calculated ratio are calculatedwith respect to a gap in each plasma process. Then, the appropriatefirst dielectric member 55 is provided at the appropriate position, sothat plasma distribution in the processing space PS can be optimizeddepending on different processing conditions for different processingpurposes.

By optimizing the plasma distribution in the first processing space PS,in-plane uniformity of an etching rate can be expected.

In the present embodiment, a ring-shaped second dielectric member may befurther provided at the shower head 51's side surface facing the firstdielectric member 55. In this case, an overlap area between the firstdielectric member 55 and the second dielectric member may be changedaccording to movement of the shower head 51. Accordingly, a range of achange in the electrostatic capacitance of the electrostatic couplingdepending on movement of the shower head 51 becomes narrower, and, thus,plasma distribution in the processing space PS according to a change inthe gap can be more finely adjusted.

Further, in this case, cross sections of the first dielectric member 55and the second dielectric member along the central axis of the chamber11 may have a rectangular shape or a triangular shape and a thickness ina direction orthogonal to the central axis may be constant or graduallychanged along the central axis. By arbitrarily combining shapes of thecross sections of the first dielectric member 55 and the seconddielectric member along the central axis of the chamber 11, thecapacitance of the second ground path according to the change in the gapcan be varied. Therefore, a variation of the electrostatic coupling isincreased in the third embodiment.

In the present embodiment, each of the first dielectric member 55 andthe second dielectric member may be made of quartz, ceramic or aninsulating resin. Since these materials have a resistance toion-sputtering as well as a resistance to radicals, the first dielectricmember 55 and the second dielectric member can be prevented from beingeroded by plasma generated in the first processing space PS. Theceramic-based material may include, for example, alumina ceramic,aluminum nitride, silicon nitride, yttria (Y₂O₃), sapphire, andzirconia, and the insulating resin may include, for example,polytetrafluoroethylene.

In the above-described third embodiment, it has been described that theshower head 51 moves, but the susceptor 12 may be moved. In this case,the first dielectric member is provided at the chamber 11's sidewall 53facing a sidewall of the susceptor 12, and an electrostatic coupling isformed between the susceptor 12, the first dielectric member 55, and thesidewall 53 of the chamber 11. Accordingly, an overlap area between thesusceptor 12 and the first dielectric member 55 is changed according tomovement of the susceptor 12. Therefore, an electrostatic capacitance ofthe electrostatic coupling is changed, so that plasma distribution inthe first processing space PS can be optimized.

FIGS. 8A to 11D show modified examples of an electrostatic couplingbetween the shower head 51, the first dielectric member 55, and thesidewall 53 of the chamber 11 in the third embodiment.

As depicted in FIGS. 8A to 8D, in an electrostatic coupling forming asecond ground path, a first dielectric member 65 is provided at asidewall 63 of a chamber 11 and has a rectangular cross section along ancentral axis of the chamber 11 and serves as a part of a dielectricmember of a capacitor in the same manner as illustrated in FIGS. 7A to7D.

In a status where a shower head 51 is at the lowermost position (seeFIG. 8A), an overlap area between the shower head 61 and the firstdielectric member 65 becomes 0. In a status where the shower head 61arrives at the middle point between the lowermost position and theuppermost position (see FIG. 8B) by gradually moving upward, an overlaparea between the shower head 61 and the first dielectric member 65becomes 0.5 times of an overlap area when they face each other with fulloverlap (see FIG. 8C). Further, in a status where the shower head 61arrives at the uppermost position (see FIG. 8C), the shower head 61 andthe first dielectric member 65 face each other with full overlap and anoverlap area becomes largest. In this case, as depicted in FIG. 8D, anelectrostatic capacitance becomes gradually decreased in a sequence ofFIGS. 8A, 8B, and 8C. As the electrostatic capacitance is changed, acapacitance of the second ground path flowing through the sidewall 63 ofthe chamber 11 to a ground is changed. Therefore, a value of a highfrequency current flowing through a peripheral end portion of the showerhead 61 is changed, so that plasma distribution in the processing spacePS becomes optimized.

FIGS. 9A to 9D show that a second dielectric member 76 is provided at aside surface of a shower head 71 in addition to a first dielectricmember 75 and an overlap area between the first dielectric member 75 andthe second dielectric member 76 is changed in the same manner asillustrated in FIGS. 8A to 8D. In this modified example, as depicted inFIG. 9D, an electrostatic capacitance of an electrostatic couplingforming a second ground path is decreased in a sequence of FIGS. 9A, 9B,and 9C, but each value of the electrostatic capacitance and a decreasingrate are lower than those of FIGS. 8A to 8D.

In FIGS. 10A to 10D, there has been employed a first dielectric member85 having a right triangular cross section instead of the firstdielectric member of FIGS. 8A to 8D. The right triangular cross sectionhas a half area of a cross section area of the first dielectric memberalong the central axis of the chamber 11 and has a thickness which isgradually decreased toward the lower side FIGS. 10A to 10D. In thismodified example, an overlap area between the first dielectric member 85and a side surface of a shower head 81 is changed in the same manner asillustrated in FIGS. 8A to 8D. However, since the thickness of the firstdielectric member 85 is decreased toward the lower side, anelectrostatic capacitance of an electrostatic coupling forming a secondground path is decreased in a sequence of FIGS. 10A, 10B, and 10C and adecrease amount is greatly changed in a curve shape.

Further, in FIGS. 11A to 11D, there have been employed first and seconddielectric members 95 and 96 each having a right triangular crosssection as shown in FIGS. 10A to 10D instead of the first and seconddielectric members of FIGS. 9A to 9D. In this modified example, asdepicted in FIG. 11D, an electrostatic capacitance of an electrostaticcoupling forming a second ground path is decreased in a sequence ofFIGS. 11A, 11B, and 11C and a decrease amount is changed in a curveshape.

In accordance with the modified examples of the present embodiment,depending on a change in a gap caused by movement of a shower headserving as a movable electrode, a position, a shape of a cross section,and a thickness of an appropriate dielectric member are selected and,then, the dielectric member is provided at the selected position.Accordingly, plasma distribution in the first processing space PS foreach plasma process condition can be optimized and a capacitancedistribution ratio of a ground path may be added to parameters foradjusting the plasma distribution.

What is claimed is:
 1. A substrate processing apparatus comprising: acylindrical shaped chamber configured to accommodate a substrate,including a sidewall and a cover; a movable electrode capable of movingalong a central axis of the cylindrical shaped chamber within thecylindrical shaped chamber, the movable electrode being an upperelectrode; a facing electrode facing the movable electrode within thecylindrical shaped chamber, the facing electrode being a lowerelectrode; and an expansible/contractible partition wall connecting themovable electrode with an end wall on one side of the cylindrical shapedchamber, wherein a high frequency power is applied to a first spacebetween the movable electrode and the facing electrode, a processing gasis introduced thereto, and the movable electrode is not in contact withthe sidewall of the cylindrical shaped chamber, a first low dielectricmember is installed on a top surface of the movable electrode facing asecond space between the movable electrode and the cover of thecylindrical shaped chamber, and a second low dielectric member isinstalled on a bottom surface of the cover facing the second space, avoltage drop at the second space caused by the high frequency power isadjusted by the first low dielectric member and the second lowdielectric member to suppress generation of plasma in the second space,the second low dielectric member is formed of a plate shaped member, andthe first low dielectric member is formed by stacking two sheets of theplate shaped member, and the voltage drop at the second space isdecreased by increasing a voltage drop at the first low dielectricmember or by increasing a voltage drop at the second low dielectricmember, thereby reducing a potential difference in the second space. 2.The substrate processing apparatus of claim 1, wherein a dielectricconstant of each of the first low dielectric member and the second lowdielectric member is about 10 or less.
 3. The substrate processingapparatus of claim 2, wherein each of the first low dielectric memberand the second low dielectric member is made of polytetrafluoroethylene(PTFE), a copolymer of tetrafluoroethylene and perfluoroalkyl vinylether (PFA) or polychlorotrifluoroethylene (PCTFE).
 4. The substrateprocessing apparatus of claim 1, wherein another dielectric member isfurther installed between the sidewall of the cylindrical shaped chamberand the movable electrode.
 5. The substrate processing apparatus ofclaim 4, wherein a thickness of the another dielectric member is equalto or greater than about 5 mm in a direction from the movable electrodeto the sidewall.
 6. The substrate processing apparatus of claim 4,wherein the another dielectric member is made of ceramic.
 7. Thesubstrate processing apparatus of claim 4, wherein the anotherdielectric member is installed at the movable electrode.
 8. Thesubstrate processing apparatus of claim 4, wherein the anotherdielectric member is installed at the sidewall.
 9. The substrateprocessing apparatus of claim 1, wherein the plate shaped member has athickness of about 1 mm.